Any idea why voodoo charges more for a AMD Athlon XP processor than a Athlon 64 3200+? Also i thought that the higher the number the more Ghz's? So why are the faster processors less?

AMD Athlon 64 Processor 3200+(No charge)
AMD Athlon XP Processor 2500+ $446.78
AMD Athlon XP Processor 2800+ $332.06
AMD Athlon XP Processor 3000+ $243.23